Features: produced in the grinding process, there are almost parallel short cracks or network cracks on the tooth surface. Parallel cracks are usually deeper than net cracks. Grinding cracks are generally shallow and hard to be found by naked eyes, which can only be detected by magnetic particle inspection or treatment with 5% nitric alcohol corrosive solution. Sometimes grinding cracks are potential, which can only be revealed after idle time or loading.
Cause: it is mainly caused by the heat in the grinding process, or it may be caused by the unreasonable heat treatment process (the metallographic structure sensitive to grinding overheating is formed in the heat treatment process). Grinding overheating may be due to improper selection of grinding process parameters, unqualified or improper selection of grinding wheel, improper cooling measures, etc. Some gear materials sensitive to grinding overheating are more likely to produce grinding cracks.
Preventive measures: select appropriate grinding process, control feed rate and grinding speed, strengthen cooling measures, select materials that are not easy to grind and appropriate heat treatment process. Appropriate grinding wheel shall be selected, and attention shall be paid to its trimming and balancing; grinding wheel with intermittent working surface shall be used to reduce the thermal stress of surface layer.